Disclosure statement

Catherine Gautier-Downes has received funding from the US government, NASA, NSF, NOAA, DoE, and is a former volunteer science adviser to 350.org.

Frank Jotzo has received funding from various organisation, and holds various positions related to climate change policy

Katharine Hayhoe is the founder and CEO of ATMOS Research, and regularly receives US federal funding and foundation grants. She is a science advisor for Citizen’s Climate Lobby and the Energy & Enterprise Institute.

Matt McDonald has received funding from the UK’s Economic and Social Research Council.

Pep Canadell receives funding from the Australian government.

Cathy Alexander, Clive Hamilton, David Hodgkinson, Jessica Hellmann, Peter Christoff, and Robyn Eckersley do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

After two weeks of negotiations in Paris, the world’s nations have reached a global deal to tackle climate change (read the text here). The agreement commits 196 countries to help limit global warming to “well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃”.

The national targets will be reviewed and strengthened every five years.

Global emissions should peak “as soon as possible”.

By the second half of this century, greenhouse gas emissions should be balanced out by sinks, processes that remove them from the air.

Developed nations will contribute at least US$100 billion a year from 2020 to help poorer nations deal with climate change.

Below, our experts react to the agreement:

Robyn Eckersley, Professor of Political Science, University of Melbourne

The signature achievement of the Paris Agreement is a much bolder temperature target than expected: a ceiling of 2℃ warming, plus the pursuit of the safer target of 1.5℃.

Yet the parties have formally acknowledged that the 185 national pledges submitted thus far for the post-2020 period are well short of what is required to prevent dangerous climate change. The success of the Paris Agreement will therefore turn on how quickly the parties are able to ratchet up their ambition over time.

The good news is that the parties have agreed to relatively short, five-yearly cycles of nationally determined contributions. They have also agreed that each successive contribution shall be a progression beyond the previous one and reflect each party’s highest possible ambition.

The bad news is that there is no requirement that the parties must review and upgrade their existing pledges before 2030, although they may voluntarily choose to do so at any time.

On a worst-case scenario, we could see no ratcheting up of pledges over the next 15 years, just as we have seen no shift in the Copenhagen 2020 pledges made in early 2010. This would require much more heroic efforts in subsequent cycles and make it much harder to reduce the risks of dangerous warming.

However, the worst-case scenario is unlikely. There will be a facilitative dialogue in 2019 to take stock of collective effort, and we can expect some parties to upgrade their existing pledge.

In 2020, parties are required to communicate their next round of contributions for the post-2025 and 2030 periods. Parties are also urged to formulate long-term emission reduction strategies. This will exert further pressure on parties to lift their horizons and their game.

Together these various provisions provide a clear signal for everyone, but especially the business community: there is only one direction for emissions to go, and that is down, and the faster the better.

Clive Hamilton, Professor of Public Ethics, Centre For Applied Philosophy & Public Ethics, Charles Stuart University

Twenty-three years after signing the UN Framework Convention on Climate Change, the nations of the world have at last decided to act on it. The Paris Agreement will mark a turning point in so many ways and represents a victory that would have seemed impossible even one or two years ago.

We knew coming into the conference that the global emissions pathway embodied in the agreement would fall well short of what the science tells us is needed to avoid dangerous climate change. We remain on track for an Earth that will be three or so degrees warmer – a world that must be avoided at all costs.

Before they came to Paris, countries had made their pledges for the next 10-15 years and they were not up for negotiation. So what was always at stake in Paris was how far the outcome would go to reflect new realities, consolidate progress and, critically, define a mechanism for much deeper emission cuts over the next decade or two.

Assessed in these terms, the Paris Agreement is as good as could be hoped for. Two or three years ago the inclusion of an ambition to “pursue efforts to limit the temperature increase to 1.5℃” would have been unthinkable.

While the Agreement does not acknowledge the severely constrained carbon budget, the commitment to global peaking of emissions “as soon as possible … and rapid reductions thereafter” reflects a new urgency.

The decisive question now is how powerfully the Paris Agreement will signal to those outside national governments, including business, that the world has entered a new era. Because it is what they do over the next few years that will determine how deep the next round of emission cuts can be. All the indications are that Paris will send a very strong signal indeed.

Peter Christoff, Associate Professor, School of Geography, University of Melbourne

2015 is set to be the hottest year ever recorded. Appropriately, the Paris Agreement contains the strongest temperature goal of any international climate deal so far. Its aims - to strengthen global action to hold warming well below 2℃ and encourage efforts to limit warming to 1.5℃ - frame and drive the Agreement’s ambition.

Robust reference to 1.5℃ was strongly contested and opposed by Saudi Arabia, China, India and some other developing countries as an impediment to their development.

By contrast, the United States and the European Union joined a broad “coalition of high ambition” championed by the small island states, and enthusiastically sought tougher phrasing.

Some are sceptical about why they did so. To quote one negotiator: “The inclusion of these targets merely recognizes the desperate need of climate-vulnerable states, buys their support, weakens their resistance on other issues, and helps split the developing state bloc.”

Such cynicism misses the point. The new goal is not empty symbolism. It is still achievable and has beneficial real-world implications. It ramps up urgency, strengthens expectations for rapid mitigation by governments and the private sector, and intensifies pressure for funding transfers to the developing world. (The Agreement also calls for a new IPCC report in 2018 to look at mitigation pathways associated with achieving 1.5℃.)

Inevitably, many provisions in the final text remain insufficient. For example, the deal acknowledges the emissions gap between the currently inadequate national climate pledges and its goal but does not press for the full implementation of even these pledges nor requires their strengthening before 2025. It seeks a balance of emissions and removals of greenhouse gases “in the second half of this century” yet it merely calls for global emissions to peak “as soon as possible”. Its climate finance clauses are dilatory and enhanced contributions to the Green Climate Fund will not be required before 2025.

These limitations must be overcome if we are to meet this historic Agreement’s aim of “significantly reducing the risks and impacts of climate change”.

Pep Canadall, Executive Director of the Global Carbon Project, CSIRO

By many accounts the Paris climate agreement is an extraordinary achievement. It cements the long-term goal of staying under 2°C above the preindustrial Era. However, it falls short from providing specific mitigation milestones to ensure we will be tracking compatible emission pathways in the long journey to the end of the century. The statement of balancing greenhouse gases emission and sinks during the second part of the century is too ambiguous; achieving this goal towards the end of the century would most certainly take the planet above 2°C.

Frank Jotzo, Director, Centre for Climate Economics and Policy, Australian National University

The Paris agreement is a framework for ambitious long term global climate policy. The remarkable achievement of this agreement is that it spells out strong global ambition, a mechanism to move towards meeting that ambition, and universal participation by all countries.

The goal to keep global warming to well below 2℃ and pursue efforts to limit it to 1.5℃ is the right one in light of the science, though it is aspirational given the dwindling global carbon budget. A massive commitment gap exists between this new global goal and the national pledges on the table now. The Paris Agreement provides a useful mechanism for ratcheting up countries’ emissions targets in five-yearly reviews.

Whether the high global goal can be met is unclear, but the world can do much better than the pledges that are on the table now. Decarbonisation is increasingly seen as inevitable. It can be an enabler of sustained economic growth, and is in line with other objectives such better air quality and energy access. And achieving emissions reductions tends to be easier and cheaper than expected, in part because of rapid improvements in low carbon technologies.

Australia played a constructive role in the negotiations. In Paris there was a sense that “Australia is back”. The government’s emphasis on innovation is helpful, as is the commitment to double public funding for clean energy R&D. But the real test will be the review of policies announced for 2017, and the revision of Australia’s national emissions target.

Loss and damage

Matt McDonald, Associate Professor of International Relations, University of Queensland

The issue of loss and damage – the significant costs of unavoidable climate impacts such as sea-level rise, particularly experienced by vulnerable states – emerged as a key point of contention in negotiations in Paris. While vulnerable countries pushed for the inclusion of loss and damage in the agreement, it was opposed by some developed states, most notably the United States, which was concerned that the loss and damage agenda would expose American businesses to law suits for their role in contributing to climate change.

Ultimately, loss and damage has found its way into the final text as Article 8. And the Warsaw International Mechanism, established in 2013 as an instrument to assess and respond to loss and damage, is to continue. Article 8.2 also allows this mechanism to be enhanced and strengthened through subsequent negotiations.

The final text rules out liability or compensation arising from loss and damage, an inclusion that reflects American concerns. But the inclusion of loss and damage is still significant. It is the first time loss and damage has appeared in an international climate agreement, and is ultimately recognition of the inevitability of climate impacts and their disproportionate effects on the world’s poorest.

David Hodgkinson, Associate Professor, University of Western Australia

Loss and damage is also an issue of “climate justice” or legal liability.

At COP19 in 2013 a mechanism for loss and damage associated with climate change impacts was established. That mechanism will now continue beyond 2016. The Paris Agreement, however, represents no real or substantive advance on COP19.

The COP 21 decision establishes a clearinghouse for risk transfer matters and information that will serve as a repository for insurance and risk transfer information, and a taskforce to develop recommendations to address climate change displacement.

Importantly, the COP also agrees that Article 8 of the Paris Agreement “does not involve or provide a basis for any liability or compensation”. Article 8 provides that parties should cooperatively enhance understanding, action and support regarding loss and damage and sets out areas of cooperation and facilitation. And that’s pretty much it.

A report this year found that developing countries will face US$1.7 trillion each year in just economic damage annually by 2050 if global average temperatures rise by 3℃.

In that and other contexts, the decision and the agreement made at COP21 go only a small way to address loss and damage issues.

Climate adaptation

Jessica Hellmann, Director, Institute on the Environment, University of Minnesota

The Paris Agreement largely focuses on the adoption of national pledges towards greenhouse gas mitigation, but it has quite a lot to say about the importance and demand for adaptation.

The Agreement emphasises the need for communication and collaboration among countries toward achieving adaptation, particularly in the developing world where the impacts of climate change will be felt most strongly and who have limited structures in place to adjust to those impacts. It calls for methods to assess adaptation needs by countries leading to recommendations for adoption in future negotiations; it directs all agencies to include climate change resilience in its development aid; and it calls for continued implementation of national adaptation plans.

The Agreement further recognises that climate change will cause loss and damage to countries around the world, but it does not allow for financial compensation for those losses. Adaptation assistance from developed countries, therefore, follows not from formal responsibility but from a desire to assist developing countries. This is a subtle but important distinction with potential implications for the amount and source of money from wealthier to poorer countries. In an effort to grow developed countries’ financial commitments, however, the agreement calls for a minimum investment of US$100 billion a year by 2020 towards both mitigation and adaptation for developing countries.

That adaptation is such a recognised component of the agreement is a step in the right direction, yet the Agreement shows how much remains unknown about the extent of adaptation needed, its best practices, and how to ensure its public and private financing. While exciting to have an agreement in hand that commits to fundamental principles, much remains to be done.

Emissions reductions

What does this agreement mean in terms of world emissions by mid-century? Clearly, the climate pledges made by more than 180 countries do not align with the mandate to limit Earth’s warming to 1.5℃ by 2100 to limit climate risks. They would lead to 2.7 or 3℃. The agreement offers no alternative trajectory to get the world to 1.5ºC.

It is probably outside the agenda for solutions that emission reductions will be found, through:

the renewable energy “revolution” underway with 2015 investments in renewable higher than in fossil fuels in the world and in the developing countries and, in the future, illustrated by the International Solar Alliance to expand solar development to 100 terawatts;

The pledge by 700 mayors to reduce emissions from consumption and increase the share of renewable by 50% by 2050;

the multiple financial pledges that come to nearly US$80 billion;

the financial and business sectors’ new engagement and demand for a carbon price, including the growing movement for fossil fuel divestment;

Drastically cutting emissions in the near term is crucial but not enough without “negative” emissions. Opportunities for negative emissions in the building or forest sectors, for instance, must be central research topics in the coming years. This COP is a historic moment that represents a global power shift and puts the world on the path to the fully carbon neutral and climate-resilient world our children and grandchildren deserve.

For a climate scientist who’s spent over a decade on the front lines, the Paris Agreement it is like finding out the biggest and most ambitious grant proposal of your career has been funded.

It limits warming not just to 2℃, but possibly 1.5℃; it sets a goal of bringing net emissions into balance within a matter of decades, not centuries; and it establishes the framework to provide tangible assistance to the poorest nations, including both finance and technology. This plan fulfils the vision of the United Nations Framework Convention on Climate Change: it will significantly reduce the risk dangerous human interference with the climate system.

As with an ambitious grant, though, euphoria will soon give way to speculation. Will we accomplish all we promised? And if so, how?

The Paris Agreement is not naïve: the majority of its 31 pages lays out the need for ongoing reporting, special IPCC reports, financing for the Green Climate Fund, even naming individual climate Champions, tasked with keeping the process moving. To succeed, it will need all the help it can get; but if it does, all of our work – in climate science, policy, impacts, law, communication, and many other fields – will have not been in vain.

The head of the UN climate summit banged his gavel to approve this new deal at 7.27pm – and it’s a climate denier’s worst nightmare.

Footage of delegates and ministers cheering and hugging will go around the world and be remembered for years. This deal will be seen as a success: every country is on board with an ambitious climate deal.

Politically, that’s game-changing. What happens next is that pressure will mount on every government – particularly developed countries – to do more on climate change. The text talks about capping global warming at 1.5℃; there’s not a single developed country with a target strong enough to do that. So this deal makes it easier for any government to put out stronger climate targets and policies. It’s now much harder for governments to lag behind or stick with what they have. The well-worn claims that “others aren’t acting” and “the world can’t agree” have gone.

Watch the pressure mount on governments to ramp up their targets and policies. Watch the numbers being crunched on what countries’ emissions targets should be to meet 1.5℃. Watch the environmentalists mobilise.

Those who want action on climate change have had their hands strengthened tonight.